AS HE SITS comfortably on the sofa in his Lowell House common room, senior Bruce G. Sabath's eyes light up only faintly when he speaks of his current role as Tevye in Fiddler on the Roof. Their captivating brilliance is reserved for his actual presence on stage.

Opening last Thursday night at Kirkland House and finishing with two shows tonight, Fiddler has received both standing ovations and rave reviews. The musical and acting ability of the cast deserves much acclaim, but the success of any production of Fiddler depends on the strength of the leading character, Tevye, who confides in God and the audience. According to director Grick Neher, "If the Tevye is strong, then the play is strong. If the Tevye is weak, then the play is weak." In this production of Fiddler the Tevye is very strong.

Sabath's powerful performance stems from his acting experience while in high school. In his freshmen year at Harvard, Sabath played a minor role as an evil merchant in Aladdin at the Agassiz, but in high school Sabath played such roles as Faggin in Oliver Twist, Bottom in A Midsummer Night's Dream, and surprisingly, but yet not so surprisingly, Tevye. Of all these roles, Sabath says he favors the role of Tevye.

"Tevye is a well-developed character," Sabath explains. "He's a happy character with a good sense of humor but he also has a dark side which comes across as his emotional side in the play." Sabath adds both his sense of humor and his strong emotions allow him to adjust to the whole world falling apart around him. He is the one who is forced to deal with change when the other characters don't realize what is happening.

In photographs of his high school's production of Fiddler, Sabath looks almost the same as he does on stage at Kirkland House five years later. He wears the same rust vest and flannel shirt belonging to his father. Although the Tevye's of then and now may appear similar, Sabath's portrayal of them is not the same. "Since I had already learned the lines I was able to concentrate more on the character and what he was experiencing," Sabath notes.

Sabath's "concentration" on the character results in a convincing portrayal of an elderly Jewish dairyman--the family's papa and the audience's hero. The ever-bending posture, the gestures, the accent, never let the audience remember the actor's true age of 21. Sabath says he uses his grandfather, who died when Sabath was only seven, as a role model for playing Tevye. Like Tevye, Sabath's grandfather was a dairymen in Russia, who came to America in the early twentieth century. Unlike Tevye, and fortunately as well, Sabath's grandfather left the Ukraine without being forced to leave.

"A lot of the accent was from him. In playing Tevye I just kept thinking how hard he worked and how tired he was. But he was always in a good mood. He was a great guy. And like Tevye he believed in upholding traditions," Sabath says.

Relying on personal experience, Sabath adds that he purposely steered his portrayal of Tevye away from Zero Mostel's acclaimed rendition of the character. "I think that Mostel perhaps did a little too much comedy with Tevye. He played him too much like a clown so that the audience was laughing at him rather than with him. I try to play the character with a little more pathos."

IN HIS LAST TERM at Harvard, when Sabath is not on stage in Fiddler, or T.F.ing a course in information theory, he sings bass with the five-year-old Din and Tonics, one of two all-male a capella groups on campus. The Dins perform about 60 concerts a year and have traveled to Bermuda three times. Sabath considers singing with the Dins "the greatest part of my Harvard experience," providing him with an outlet for his love of the stage.

Like most who love performing Sabath has toyed with the idea of becoming a professional actor. "But doing a show over and over again--it gets numbing. My longest run was eight shows. After 400 it becomes a job. After graduating Sabath plans to live in Manhattan and work at a computer firm. He doesn't foresee, however, totally giving up performing. Sabath plans to form an a capella quartet with some fellow graduates, the new group will reintroduce New York to the tunes of the forties.

And if Sabath was offered the role of his choice? "I would play Tony in West Side Story. It's a romantic lead--a character part. And the play has such beautiful songs....Only the role is for a tenor. I would like to play Tevye again...."